webhooks/jira: Handle anomalous payloads properly.

We recently ran into a payload in production that didn't contain
an event type at all. A payload where we can't figure out the event
type is quite rare. Instead of letting these payloads run amok, we
should raise a more informative exception for such unusual payloads.
If we encounter too many of these, then we can choose to conduct a
deeper investigation on a case-by-case basis.

With some changes by Tim Abbott.

zerver/webhooks/github/view.py

@@ -4,7 +4,7 @@ from typing import Any, Callable, Dict, Optional
 
 from django.http import HttpRequest, HttpResponse
 
-from zerver.decorator import log_exception_to_webhook_logger, webhook_view
+from zerver.decorator import log_unsupported_webhook_event, webhook_view
 from zerver.lib.exceptions import UnsupportedWebhookEventType
 from zerver.lib.request import REQ, has_request_variables
 from zerver.lib.response import json_success
@@ -45,9 +45,8 @@ class Helper:
 
     def log_unsupported(self, event: str) -> None:
         summary = f"The '{event}' event isn't currently supported by the GitHub webhook"
-        log_exception_to_webhook_logger(
+        log_unsupported_webhook_event(
             summary=summary,
-            unsupported_event=True,
         )